Attentive readers might already know the concept of "edge bundling" as described in a post almost 2 years ago, and more recently exemplified by the Eigenfactor Citation Patterns graph. Edge bundling is based on the principle of visually bundling adjacency edges together, analogous to the way electrical wires and network cables are merged into bundles along their joint paths, and then fanned out again at the end, in order to make an otherwise tangled web of wires and cables more manageable. When applied to the field of data visualization, this technique can be used in conjunction with several existing data mapping techniques to significantly reduce visual clutter.
Danny Holten and Prof. van Wijk have recently succeeded to merge the concept of edge bundling with force-directed network graphs, also known as node-link graphs, in their work "Force-Directed Edge Bundling for Graph Visualization". Here, edges have been modeled as flexible springs that are able to attract each other. The resulting network visualizations show significantly less clutter while making high-level edge patterns more visible.